Conditional expression of apical membrane antigen 1 in Plasmodium falciparum shows it is required for erythrocyte invasion by merozoites.

Malaria is caused by obligate intracellular parasites, of which Plasmodium falciparum is the most lethal species. In humans, P. falciparum merozoites (invasive forms of the parasite) employ a host of parasite proteins to rapidly invade erythrocytes. One of these is the P. falciparum apical membrane antigen 1 (PfAMA1) which forms a complex with rhoptry neck proteins at the tight junction. Here, we have placed the Pfama1 gene under conditional control using dimerizable Cre recombinase (DiCre) in P. falciparum. DiCre-mediated excision of the loxP-flanked Pfama1 gene results in approximately 80% decreased expression of the protein within one intraerythrocytic growth cycle. This reduces growth by 40%, due to decreased invasion efficiency characterized by a post-invasion defect in sealing of the parasitophorous vacuole. These results show that PfAMA1 is an essential protein for merozoite invasion in P. falciparum and either directly or indirectly plays a role in resealing of the red blood cell at the posterior end of the invasion event.

Essential Role of the PfRh5/PfRipr/CyRPA Complex during Plasmodium falciparum Invasion of Erythrocytes.

Plasmodium falciparum parasites in the merozoite stage invade human erythrocytes and cause malaria. Invasion requires multiple interactions between merozoite ligands and erythrocyte receptors. P. falciparum reticulocyte binding homolog 5 (PfRh5) forms a complex with the PfRh5-interacting protein (PfRipr) and Cysteine-rich protective antigen (CyRPA) and binds erythrocytes via the host receptor basigin. However, the specific role that PfRipr and CyRPA play during invasion is unclear. Using P. falciparum lines conditionally expressing PfRipr and CyRPA, we show that loss of PfRipr or CyRPA function blocks growth due to the inability of merozoites to invade erythrocytes. Super-resolution microscopy revealed that PfRipr, CyRPA, and PfRh5 colocalize at the junction between merozoites and erythrocytes during invasion. PfRipr, CyRPA, and PfRipr/CyRPA/PfRh5-basigin complex is required for triggering the Ca(2+) release and establishing the tight junction. Together, these results establish that the PfRh5/PfRipr/CyRPA complex is essential in the sequential molecular events leading to parasite invasion of human erythrocytes.

A novel treatment approach for low grade lymphoproliferative disorders using PKC412 (CGP41251), an inhibitor of protein kinase C.

INTRODUCTION: PKC412 (formally CGP41251) selectively inhibits protein kinase C (PKC) isoforms and has been shown to be cytotoxic to malignant cells in vitro. We have undertaken a single centre, open-label, multi-dose, exploratory Phase II clinical trial of PKC412 in patients with CLL and low grade NHL. METHODS: Thirteen CLL patients and eight stage IV NHL patients were treated at three oral dose levels of 25, 150 and 225 mg/day for 14 days. RESULTS: There was a median decrease of 29.4% in the lymphocyte count in 11 out of 18 patients with circulating disease following treatment. Two NHL patients without circulating disease showed loss of immunophenotypic evidence of marrow disease and a third showed an improvement in blood counts and transfusion requirements. Adverse events were mostly gastrointestinal (16 patients) requiring little or no intervention. In nine patients there was an asymptomatic rise in serum amylase and/or transaminases. Asymptomatic hyperglycemia was also observed in eight patients. All returned to normal following cessation of treatment. In 14 out of 20 patients total PKC activity measured in peripheral blood and/or bone marrow lymphocytes was reduced during treatment to a mean of 54% of pre-treatment level. CONCLUSION: PKC412 is safe, well tolerated and reduces the tumor load in chronic B-cell malignancies. Inhibition of PKC offers a novel approach to the chemotherapy of B-cell malignancies.

Insights and controversies into the role of the key apicomplexan invasion ligand, Apical Membrane Antigen 1.

Apicomplexan parasites are obligate intracellular pathogens that cause a host of human and animal diseases. These parasites have developed a universal mechanism of invasion involving formation of a 'moving junction' that provides a stable anchoring point through which the parasite invades host cells. The composition of the moving junction, particularly the presence of the protein Apical Membrane Antigen 1 (AMA1), has recently been the subject of some controversy. In this commentary we review findings that led to the current model of the moving junction complex and dissect the major conflicts to determine whether a substantial reassessment of the role of AMA1 is justified.

Evaluation of buccal alveolar bone dimension of maxillary anterior and premolar teeth: a cone beam computed tomography investigation.

PURPOSE: Clinical guidelines suggest that a minimal buccal alveolar bone thickness of 1 to 2 mm is required to maintain the tissue architecture following tooth extraction and implant placement. The aim of this study was to evaluate the thickness of buccal alveolar bone at the maxillary first premolars and anterior teeth using cone beam computed tomography (CBCT). MATERIALS AND METHODS: CBCT images of the maxillae of 43 implant patients were obtained. Two examiners manually measured the distance from the cementoenamel junction (CEJ) to the buccal alveolar bone crest and the thickness of the buccal alveolar bone at the crest, midroot, and apex of the maxillary first premolars and anterior teeth. The absence of bone and presence of radiographic artifacts were recorded. Average bone thicknesses were calculated and compared. Both parametric and nonparametric statistics were used to analyze the findings. RESULTS: The median distance from the CEJ to the buccal alveolar bone crest was 2.79 mm, and measurements were similar among tooth positions. The median buccal alveolar bone thickness 1 mm apical to the alveolar bone was 1.13 mm in the premolar area and 0.83 mm for the anterior maxillary teeth. The median buccal alveolar bone thickness at the midroot was 1.03 mm in the premolar area and 0.70 mm for the other anterior maxillary teeth. Measurements of the buccal plate at 1 mm from the tooth apex were similar in all teeth positions, with a median thickness of 0.88 mm. CONCLUSIONS: The presence or absence of buccal alveolar bone can be discerned by CBCT evaluation. Few maxillary anterior teeth displayed buccal alveolar bone thickness greater than 1 mm. The implications for implant therapy must be fully discerned regarding tissue biotypes and dental implant outcomes.

Dental implants in patients with ectodermal dysplasia and tooth agenesis: a critical review of the literature.

PURPOSE: The aims of this article are to critique the available literature on dental implants in patients with ectodermal dysplasia (ED) syndrome and tooth agenesis, review the outcomes of implant therapy in these patients, and provide recommendations on the timing of implant placement for these patients. MATERIALS AND METHODS: Searches were performed using Medline, Embase, All EBM Reviews, and Pre-Medline for articles relating to implant patients suffering from ED. Articles unrelated to the topic of dental implants in patients with ED and tooth agenesis, without abstracts, or in languages other than English were excluded. Selected articles were graded according to levels of evidence based upon guidelines set forth by the Agency for Health Care Policy and Research. Articles found to have a level of evidence of IV were excluded from this study. RESULTS: The literature on dental implants in patients with ED and tooth agenesis was found to be scarce. No randomized controlled or case-controlled studies were found. Only 12 articles were found to satisfy all inclusion criteria. CONCLUSION: Implant survival rates vary between 88.5% and 97.6% in patients with ED and between 90% and 100% in patients with tooth agenesis. Implants placed in adolescent ED patients do not have a significant effect on craniofacial growth, while implants placed in ED patients younger than 18 years have a higher risk of failure.